Please upload a DMX file which demonstrates this problem.

It's very difficult. You'll have to look this up online as it's a general modelling task and not related to the Blender Source Tools.

The skeleton of the mesh must be identical to the skeleton which the animation targets. You will need to change either the model or the animations to make this happen.

Please upload one of the affected DMX files.

Please upload your Blend file.

Please upload your Blend file.

That's exactly what I don't want to add.

You can disable the "Deform" option on each bone. This should already cause it to be skipped during export.

In a game, no. That's not supported.

In Source Filmmaker, yes in principle. But because the animation data format for Source Filmmaker is different from that of games, the Blender Source Tools intentionally don't target it. It's too confusing to have both at the same time.

Looks like a bad SMD file with a truncated line.